<!DOCTYPE html >
<html xmlns="http://www.w3.org/1999/xhtml">
<head lang="en">
    <meta charset="UTF-8" http-equiv="X-UA-Compatible" content="IE=Edge"/>
    <title>hello</title>
    <style>
        .aa{
            border-style: solid;
            /*background-image: url("b.png");*/
            /*background-position: 33% 33%;*/
            background-size: cover;
            /*background:linear-gradient(45deg ,red 50%,#00b3ee,#fff6de);*/
            background: radial-gradient(#fff, #64d1dd, #0000ff) no-repeat;
            width: 500px;
            height: 400px;
        }
    </style>

</head>

<body>
<div class="aa">


</div>
</body>
</html>